Russian President Vladimir Putin has started a week-long trip to Central Asia's two prime gas and oil exporters, Kazakhstan and Turkmenistan.

He is due to meet the presidents of both countries on Thursday for tripartite talks on energy supplies.

Kazakhstan has always remained quite close to Russia in its foreign policy.

The recent death of Turkmenistan's idiosyncratic president has also seemed to open the way for a return to closer relations with Russia.

Yet each of the three presidents will have different aims. For President Putin, the meeting is a chance to reinforce Russia's argument that it is the natural friend of Central Asia, not the newcomers on the scene - the West and China.

Caspian energy

Russia's is pushing the idea of a new pipeline which will carry Turkmen gas across Kazakh and Russian territory to Europe.

That would enhance Russia's already dominant position as the main route for Caspian energy supplies to the West.

Kazakh President Nursultan Nazarbayev has long lived with the need to stay close to Russia diplomatically, to keep Kazakh oil and gas flowing westward.

And he seems relaxed about continuing that way, though not averse to exploring other possibilities.

Kazakhstan already sends a significant amount of oil by ship across the Caspian, for transportation along the one major route that bypasses Russia, the Baku-Ceyhan pipeline through Azerbaijan, Georgia and Turkey.

Azerbaijan would like to expand that route further and build an under-water pipeline across the Caspian, but Kazakhstan, aware that this might seriously annoy its Russian partners, has refused to give its full support.

The real unknown in the tripartite meeting is the position of Turkmenistan's new leader, President Gurbanguly Berdymukhamedov.

Some think he is willing to revive co-operation with Russia, and go along with the pipeline through Kazakhstan.

And yet only last week, the Turkmen leader granted US oil giant Chevron access to the Turkmen sector of the Caspian Sea.